The greater jihad is the struggle against nafs. It is reported that the Messenger of Allah (peace be upon him), returning from a military campaign, said:

"We came back from the small Jihad to the great Jihad".

Here the Messenger of Allah (peace be upon him) called the fight against nafs great jihad. As: "The soul of man commands evil". Struggling agains nafs, which constantly commands bad and abstaining from its desires - it is a great thing. Therefore, Allah Almighty promised Paradise to those who oppose the bad desires of the nafs, saying in the Quran:

وأما من خاف مقام ربه ونهى النفس عن الهوىفإن الجنة هي المأوى

"But as for he who feared the position of his Lord and prevented the soul from [unlawful] inclination, Then indeed, Paradise will be [his] refuge". (The Quran, 79:40-41)